Heavy clashes broke out Thursday afternoon between gunmen and guards at the Shiite-controlled Health Ministry building in north Baghdad, security officials said.

State-run Iraqiyah television said the Health Ministry was being attacked with mortars by "terrorists who are intending to take control of the building."

The security officials said about 30 gunmen, believed to be Sunni insurgents, had launched the attack.

Iraqi troops were being rushed to the area and all roads leading to the ministry in Bab al-Muadham neighborhood were closed, said the security officials on condition of anonymity because they were not authorized to speak to reporters.

Police Lt. Ali Muhsin said the attack began at 2:10 p.m. when three mortar shells hit the building, causing damage. After that, gunmen on the upper floors of surrounding buildings opened fire. Ministry workers were trapped in the building, but there were no immediate reports of casualties.

Early Thursday morning, U.S. and Iraqi forces swept into Baghdad's Sadr City slum, killing four Iraqis, wounding eight and detaining five in the latest raid on the Shiite stronghold, police said.

Hours later, a car bomb exploded in a major Sadr City food market, killing at least 10 and wounding 15, police said. Three mortar shells crashed to earth nearby.

About 15 cars were destroyed and ambulances were racing to take away the wounded, said police Col. Hassan Chaloub.

Car bombs in Sadr City in the past months have killed and wounded hundreds.

Police Capt. Mohammed Ismail said coalition forces searched Sadr City houses at about 4:30 a.m. and opened fire on a minivan carrying Iraqi workers in the al-Fallah Street area, causing the deaths and injuries. Iraqis often pay a small fee to crowd into such vehicles and travel early in the morning to sites where they hope to be hired as day laborers.

In a statement, the U.S. military confirmed the raid and said it was conducted in the continuing effort to find an American soldier who was kidnapped Oct. 23. It confirmed that a vehicle was shot at by Iraqi forces after "displaying hostile intent," but did not report on casualties.

It was the fourth raid in six days on the slum that is home to the Mahdi Army, the militia loyal to radical anti-American Shiite cleric Muqtada al-Sadr. The Mahdi Army is suspected of kidnapping an American soldier last month and taking scores of Iraqi hostages during an attack on a government building in Baghdad on Nov. 14.

Ismail said the coalition also detained five Iraqis during the raid.

Residents of Sadr City gathered around the bloodstained, bullet-riddled minivan.

"I was surprised by the heavy shooting on our minivan. I was hit badly in my left hand," said one worker, Ahmed Gatie, 24, as he was treated at Imam Ali hospital. "I can only feed my family when I work. What will happen now?"

Witness Salah Salman, 24, said he and other local residents helped police carry victims of the attack from the minivan to the morgue and hospital.

The raid came weeks after Prime Minister Nouri al-Maliki, a Shiite, ordered the U.S. military to lift a blockade of the sprawling east Baghdad grid of streets lined with tumbledown concrete block structures and vacant lots.

American forces had sealed the district for several days looking for kidnapped U.S. soldier Ahmed Qusai al-Taayie, a 41-year-old reservist from Ann Arbor, Michigan. He was visiting his Iraqi wife in Baghdad on Oct. 23 when he was handcuffed and abducted by suspected rogue gunmen from the Mahdi Army.

Al-Sadr is a major political backer of al-Maliki, who had rejected American demands to disband the heavily armed militias and their death squads, which have carried out a brutal campaign of revenge attacks on Iraq's Sunni minority in a cycle of violence following the Feb. 22 bombing of a Shiite shrine.

But Al-Maliki has looked the other way during the most recent joint U.S.-Iraqi raids, an about-face his aides said was prompted by anger over the U.S. soldier's abduction and a mass kidnapping carried out by suspected Mahdi Army gunmen. Dozens of gunmen in police uniforms kidnapped scores of people during the raid on a Ministry of Higher Education office in Baghdad on Nov. 14. The ministry is predominantly Sunni Arab.

At least 101 Iraqis were killed Wednesday and the U.N. reported that 3,709 Iraqi civilians were killed in October, the highest monthly toll of the war and one that is likely to be eclipsed when November's dead are counted.

The United Nations Assistance Mission for Iraq also said that citizens were fleeing the country at a pace of 100,000 each month, and that at least 1.6 million Iraqis have left since the war began in March 2003.

Life for Iraqis, especially in Baghdad and cities and towns in the center of the country, has become increasingly untenable. Many schools failed to open at all in September, and professionals — especially professors, physicians, politicians and journalists — are falling to sectarian killers at a stunning rate.

Lynchings have been reported as Sunnis and Shiites conduct a merciless campaign of revenge killings.

The U.N. figure for the number of killings in October was more than three times the 1,216 tabulated by The Associated Press and nearly 840 more than the 2,870 U.S. service members who have died during the war.

The U.S. military on Thursday reported the deaths of three Marines in fighting in Anbar province, where many Sunni Arab insurgents are based.

So far this month, 52 American service members have been killed or died.